The present invention relates to pressure transmitters of the type used in industrial process control systems. More specifically, the present invention relates to a pressure sensor for use in a pressure transmitter.
Pressure transmitters are used in industrial process control systems to monitor pressures of process fluids. A pressure transmitter includes a pressure sensor which is coupled to a process fluid and provides an output in response to pressure applied by the process fluid. Two well known types of pressure transmitters is the Model 3051 and 3095 transmitters available from Rosemount Inc. of Chanhassen, Minn. Pressure transmitters are also shown in U.S. Pat. No. 5,094,109, for example.
In many installations where differential pressure is measured, it is frequently also desirable obtain a line pressure measurements (i.e., the pressure of the process fluid in the pipe or conduit) For example, the line pressure can be used for determining mass flow of process fluid, or for other control applications. However, when a line pressure measurement is required in addition to the differential pressure measurement, an additional pressure sensor is typically required. This additional pressure sensor requires additional components and coupling to the process fluid. This leads to increased complexity and expense, as well as increasing the likelihood of failure.
Further, many pressure sensing technologies are coupled to process fluid through an isolation arrangement which uses an isolation diaphragm exposed to process fluid and an isolation fill fluid which couples the pressure sensor to the isolation diaphragm. This isolation arrangement is also a source of errors, complexity, and potential failure in process devices.